Experimental study of core and edge fluctuations by reflectometry on EAST tokamak

作者：Zhou Zhen, Tao Zhang, M.F. Wu, Kaixuan Ye, Fubin Zhong, Jia Huang, Kangning Geng, Yukai Liu, Gongshun Li, H.M. Xiang, Yumin Wang, Fei Wen, Sanqiu Liu · 发表于：Plasma Science and Technology · 年份：2021 · DOI：10.1088/2058-6272/abf4b5 · 被引用次数：11 · 研究领域：Magnetic confinement fusion research、Ionosphere and magnetosphere dynamics、Superconducting Materials and Applications

Abstract An eight-channel poloidal correlation reflectometer (PCR) with O-mode polarization has been installed in the EAST tokamak to measure the fluctuations from core to edge. The PCR launches eight different frequency microwaves (20.4, 24.8, 33, 40, 42.4, 48, 52.6, 57.2 GHz) into the plasma from the low field side and two poloidally separated antennae are used to receive the reflected waves. As a result, the diagnostic can measure fluctuations in eight (radial)× two (poloidal) spatial positions. The diagnostic has been applied to study the core and edge pedestal fluctuations during an inter-ELM phase in H-mode plasma. This inter-ELM phase can be divided into two stages. In the first stage, a low frequency (<50 kHz) broadband fluctuation dominates in the pedestal gradient region. In the second stage, this fluctuation is strongly suppressed and quasi-coherent fluctuations (QCFs) appear. The QCF’s amplitude increases with the pedestal density gradient, implying density gradient driven instabilities. But the core fluctuations inside the pedestal show no evident changes during the inter-ELM phase.